This competitive revision application supports the development of Comparative Effectiveness Research for Eliminating Disparities (CERED), which includes four CERED cores: Research, Training, Data Infrastructure, and Dissemination. The research project objective is to evaluate the effectiveness of a hospital-based patient navigation intervention strategy in mammography centers located in Medically Underserved areas (MUAs) on the adequacy of diagnostic and treatment services for breast cancer care among underserved women in Chicago. Our primary research outcome will be treatment adequacy and adherence to follow-up care in women with abnormal mammograms, as defined by The National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines. This work will extend that of the ongoing comparative effectiveness research evaluating patient navigation in breast cancer care in a randomized clinical trial, in which the primary outcome is time to diagnostic resolution and treatment (Warnecke/Calhoun, P50CA106743-05;Project #1, PI: Calhoun;end date: 6/15/15). In conjunction with the existing patient navigation research project, the proposed research effort will examine comparative effectiveness of patient navigation intervention on two primary outcomes among women with abnormal mammograms (with and without breast cancer): 1) adequacy and quality of follow-up care;and 2) patient's adherence to follow-up care and treatment. The two primary hypotheses are: H 1) Navigated patients with abnormal screening results will be more likely to receive adequate diagnostic evaluations and treatment as compared to usual standard of care. H 2) Navigated patients diagnosed with breast cancer will be more likely to complete appropriate follow-up care and treatment as compared to usual standard of care. In carrying out the research project, training, data, and dissemination core activities aim to enhance scientific capital, data infrastructure, and dissemination of research findings to eliminate breast disparities.